In a communications system, when a communications connection needs to be established, control information is usually shared between communicating devices to share information needed to establish the connection. The amount of control information that is exchanged can vary depending upon the flexibility of the communications system and the needs of the connection. In an inflexible communications system with a simple connection, the control information exchanged may be small, however, when a complex connection is being established in a flexible communications system, a large amount of control information may need to be exchanged. In addition to being used to establish a connection, control information may also be needed to maintain a connection. For example, control information, including acknowledgment messages (ACK/NACK), channel quality measurements, power control commands, packet structure information, configuration instructions, and so forth, are used to maintain existing connections.
In a multi-carrier communications system, wherein there can be a degree of flexibility in the way that the communications are performed, it is important that control information be passed between communications devices to properly configure the communications connection so that both communicating devices can exchange information. For example, in some multi-carrier communications systems, it is possible to vary the number of carriers used in a communications connection, the data transmission scheme (such as CDMA or OFDM), the modulation scheme (for example, QPSK, 16QAM, 64QAM, and so on), the encoding scheme, as well as a variety of other technical aspects. If the communications devices do not share as few as one of these technical aspects while establishing the connection, it is unlikely that the communicating devices will be able to successfully share information.
A commonly used technique to exchange control information in existing communications system is to code multiplex a control channel along with data channels in an existing carrier. Since in most situations, the control channel does not consume a large amount of bandwidth, the use of code multiplexing does not negatively impact the transmission bandwidth of the carrier in a significant way.
One disadvantage of the prior art is that by code multiplexing a control channel along with data channels within an existing channel, any transmission on the data channels will need to be buffered until the control channels have been decoded. This can increase hardware requirements for communications devices as well as increase overall power consumption of the communications devices.
Another disadvantage of the prior art is that while the code multiplexing of a control channel along with data channels does not significantly impact the transmission bandwidth of the data channels, some bandwidth is lost. This can lead to increased transmission times.
Yet another disadvantage of the prior art is that sharing a single carrier does not take advantage of the frequency diversity that is available in a multi-carrier communications system. The use of frequency diversity can help to increase the probability of a successful transmission, thereby potentially increasing the network bandwidth of the multi-carrier communications system as well as reducing communications latency by reducing retransmissions.